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Running hot in the highway

9

90Pioneer

NAXJA Forum User
Location
USA
On warm days my jeep starts to run really hot. The other day I was on the highway and the temp climbed to 230* when I was going 55-60mph. So I assume this would not be an air flow blockage problem then right? The motor will get hot anytime it has to remotely work hard. Or even just idling sometimes.

Every part in my cooling system is 1 year old or less.

Does this sound like my Modine 2 core radiator is plugged up? The coolant is in execellent condition.

96 XJ AW4 4.0
 
90Pioneer said:
On warm days my jeep starts to run really hot. The other day I was on the highway and the temp climbed to 230* when I was going 55-60mph. So I assume this would not be an air flow blockage problem then right? The motor will get hot anytime it has to remotely work hard. Or even just idling sometimes.
Click to expand...

There could be a number of reasons and usually a blocked radiator core would be at the top of the list, but I doubt that's the case here.
Water pumps usually either leak from the weep hole or the shaft wears out causing the pulley to wobble, but they still pump coolant even when they're close to dying.
You could start by replacing the radiator cap. At least that's cheap and it might just work.
Another thing to look for is a plugged cat. If it's not allowing exhaust gases to escape from the engine, the engine will run hot and be lacking power. Bang the cat with your fist (preferably while it's cold) and see if it rattles like a can of marbles.
 
Add to that the lower coolant hose, does it have a spring in it ? If not it could be going flat on the hiway once it starts really moving coolant. Do you have anything blocking the radiator ? winch, is the fan shroud still on or did you toss it, if you tossed it then get another one, they need them. My 98 never gets above 210 and the only time the aux fan comes on is when my A/C works..
 
Fan shroud is still intact. Lower hose is a dealer part with a spring, about a year old. The cat is new, only about six months old.

I have an ARB bumper with a winch and lights. The winch is below the radiator and the lights I dont think block much air flow at all. I relocated my license plate which made no difference.

In the winter I had trouble with my jeep running too cold.
 
I have just went thru the same thing. Replaced the radiator. Ended up being the clutch on the fan. If you shut off the engine when it has been running at operating temperature and the fan spins still after you have some one else shut it down. The clutch is gone. It should stop with the motor if it is running at 210 or above. Check that too before you buy any more parts.
:peace: out ! WTF does that mean any way ?
:laugh2: :roflmao: :laugh2:​
 
boise49ers said:
I have just went thru the same thing. Replaced the radiator. Ended up being the clutch on the fan. If you shut off the engine when it has been running at operating temperature and the fan spins still after you have some one else shut it down. The clutch is gone. It should stop with the motor if it is running at 210 or above. Check that too before you buy any more parts.
:peace: out ! WTF does that mean any way ?
:laugh2: :roflmao: :laugh2:​
Click to expand...

Also on startup the mechanical fans generally 'roar' for about 20 seconds or so as the fluid is redistributed then they go quiet till the engine gets warmer.
 
I replaced the fan clutch about 3 weeks ago.

Pretty much every part of the cooling system has been replaced in the last year, except for the aux fan, which works great. Even both of the temp sensors, factory thermostat x 3, thermostat housing, hoses, new dealer radiator cap, etc.
 
If its hot in the summer and cold in the winter and you had the ARB bumper on both times it is blocking too much of the rad!!!

Try to find a way to allow more airflow in and around that VERY nice looking, radiator blocking bumper you have!!!

CW
 
EXACTLY what I went through just this week...

Thought that it would be the water pump since the coolant looked fine, and tested fine...radiator 1.5 yrs old.

Replaced the water pump since it was the OLDEST part in the cooling loop.

Didn't fix the problem....found out my rad cap was a 16lb not 13lb. Replaced it....helped a little bit....

Figured since it was getting hot the thermostat was shot. Bought a new one, drilled a 12 o'clock hole in it...replaced it and WALLA!

No more problems...

Work from the cheapest parts....Cap and Thermostat $15.00 total.

Water pump...$35.00

Radiator, which I didn't need. $138.00
 
*SOME* of us who have been around a while take it for granted that you used the correct thermostat the FIRST TIME.... but *SOME* people around here have this really strong propensity for REINVENTING THE WHEEL... :D
 
90Pioneer said:
I replaced the fan clutch about 3 weeks ago.

Pretty much every part of the cooling system has been replaced in the last year, except for the aux fan, which works great. Even both of the temp sensors, factory thermostat x 3, thermostat housing, hoses, new dealer radiator cap, etc.
Click to expand...
Are you burping the system after each time you do one of these things to it ? A closed system has to be burped after you get air in the system. I learned the hard way by blowing up 2 pressure bottles.
 
boise49ers said:
Are you burping the system after each time you do one of these things to it ? A closed system has to be burped after you get air in the system. I learned the hard way by blowing up 2 pressure bottles.
Click to expand...


Sorry this is on my 1996 XJ with the open cooling system.

Thermostat has been replaced 3 times in the last year, with a dealer part every time.

The bumper mounts below the radiator, it really doesnt seem like it would really block that much air flow.

The ARB on my '90 XJ never made a difference in the cooling system.
 
Dumb question, how did you set the surpentine belts tension ? Theres only one correct answer....
 
RichP said:
Dumb question, how did you set the surpentine belts tension ? Theres only one correct answer....
Click to expand...

Well I had a shop replace the radiator and water pump. The shop who did the work specializes in Jeeps only so I would hope they did it correctly. But the belt passes the good 'n tight test.
 
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